Just a little info on Loc-tite. If you ever want to get the bolt/nut/stud off again use the blue, want it on forever use the red.
Don't use regular white Teflon tape (that's for plumbing anyway) look for the yellow Teflon tape that's used for natural gas/propane/etc. Used yellow on my petcock and it's never leaked.
Teflon tape or "pipe dope" with Teflon doesn't really seal threads, NPT fittings are tapered and the Teflon acts as a lubricant so the fitting can be tightened further thus getting a better seal. The threads on the petcock and gas tank fitting are not tapered but the yellow tape is about 3x thicker then the white so it ended up making a nice gasket.